The Third Brother
by itsJooJoo
Summary: After the true pacifist is complete, Frisk lives in Toriel's house. Little does he know, the underground he saw...was only the surface of all he has to discover. Gaster returns to the underground, and things will never be the same again...
1. The Note

"Hey. Hey kid. Wake up. Dude, c'mon, we're going to be late…"

"H-huh? Wait what's going on…?"

"Did you have another bad dream…?"

Sans loomed over me as I was adjusting my eyes to the newfound light. I was in Tor-um, I mean, my house. There was yet again, a piece of butterscotch-cinnamon pie sitting next to me.

"You never cease to amaze me with your teleportation, eh Sansy?" I replied.

"Mhm" he muttered. I heard a scream from downstairs.

"Ugh, there goes Undyne freaking out over having fish for breakfast," Sans said as he got up. "Get up, or you'll have a bad time."

Here goes. I groaned as I got out of bed and walked down the halls. As I walked down the stairs, I heard a lot of chatter.

"Nyehehheheh" Papyrus laughed as Sans told him a knock-knock joke. Alphys and Undyne were watching anime while sharing a pizza. Napstablook was live-streaming Call of Dog Residue. Temmie of course was having a mental breakdown trying to see why she failed her spelling test. They all turned their heads to me as I reached the last step.

"…Hey guys…" I said while covered in sweat. Nobody replied, silence overtook the room. I started to get worried, thinking _"Did I do something wrong…?"_.

"O-Oh…man…" Sans said as he started to look around the room sheepishly. "Usually you wake up much later than this…even when I threaten you…"

"Well he's a terrible planner anyways. Sorry my child, we were preparing a party for you!" Toriel tried to explain.

"…S-surpri…surprise…?" Alphys attempted to lighten the mood up. It was no use. A sudden crash could be heard from upstairs.

"What was that?" I asked. I ran back upstairs to look in my room. The pie was gone. An eerie feeling whooshed over the room as I looked everywhere I could. A note was left on my bed.

Strange symbols that were in a seemingly random sequence were the only marks left on it. Sans teleported right behind me. His pupils dilated.

"Don't stick your nose where it doesn't belong, kiddo." He told me as he snatched the note from me. "Papyrus, you gotta see this…" he vanished. Flowey popped up soon after.

"Heh, so naïve aren't you Frisk? If only you knew what those three are up to…" He said. "…Oh…oh no…I've said too much…" He disappeared.

 _'…Three…?'_ I wondered. I had to see what's going on. I walked downstairs and I noticed everyone had a grim look on their faces.

"Gaster…Gaster is back…" Alphys whispered.

"Gaster…who's that?" I asked. Everyone's faces became more horrified.

"Oh no…please…forget you heard that…" He muttered back to me. I decided I'm going to do this on my own. As I got out, I heard somebody say something.

"Wow…I've got to see him again. I was his greatest fan…In fact…he only needs one more human SOUL…"

"H-huh!? What!?" I yelled as I started to frantically run away. I heard a slash. I felt a burning sensation in my stomach.

" **CRACK. CRICK. FWISH.** " My SOUL broke. Except, I felt empty inside. Something was…how do I put it…

"Different? Hah, your DETERMINATION is gone. And when GASTER gets his hands on you…your SAVE will be gone." The strange man finished my sentence.

The world was shaking, my head was throbbing, and my body was aching everywhere. The voice that tells me to give up…

 ** _Is gone…_**


	2. The Secret

Determination

Patience

Bravery

Integrity

Perseverance

Kindness

Justice

Of those somewhat redeemable qualities…I have none.

My mind was drifting, reality was altering, awake and asleep, alternating every minute. I could hear certain conversations in the background.

I was dying.

Everyone, all my friends…they were watching me. Speechless, the man that hurt me was—to everyone's shock—gone. I could make out some of my surroundings, I was in an ambulance, I could hear the sirens. They were screaming. I finally heard the voice.

"Don't lose hope! Stay determined!" Except…there was more…

"…Chara…please don't die…"

"Chara, we're best friends…you can't…you…you…"

I heard sobbing

"…You're gone…aren't you…?"

'Who's Chara? Am I going insane?' I thought to myself. I woke up and realized I was in the hospital. My heart was racing and I was sweating. They all followed me

…Except sans

"OH MY GOD! ARE YOU OKAY!?" Papyrus cried out. "I'M SO SORRY, SANS CALLED ME FOR SOMETHING AND"

"that's enough, pap." Sans interrupted as he seemingly appeared from thin air. "once you get healed, there's something i gotta show ya, frisk…"

"O-okay then…" I said. They took me into the ICU. I was losing my grip on reality.

"Oh my child! Please, don't go into the light!" Toriel tried to act dramatically

They all had to go into the waiting room anxiously. Flowey jumped onto my hospital bed.

"Wow. Pathetic. What's wrong with you?" Flowey scolded me. "IS YOUR DETERMINATION GONE?" He asked with a disturbingly evil face. He laughed his creepy laugh at me.

"THIS IS PROOF. HE IS BACK. HE WILL GET REVENGE ON ALPHYS." He laughed (yet again), and hopped away.

After a few days and a quick recovery, Sans came back just as I was being released.

"hey kid. c'mere, i need to show you something i regret hiding…" He informed me. We went back to Grillby's. There, he showed me that note from before. I got a clear look at it.

"It still looks like gibberish to me." I said as I attempted to analyze it.

"that's the language that gaster uses. haven't you heard of the age-old warning, 'beware of the man who speaks in hands'?" Sans explained. "SANS. PAPYRUS. PLEASE COME BACK TO THE LAB. I AM ALIVE AND WELL, PLEASE COME ASAP. THERE IS SOMETHING I NEED TO SHOW YOU!"

"Wow. How can you learn those words so quickly?" I asked.

"it's easy memorizing a language that your very brother speaks." He answered.

"Wait a minute. Papyrus doesn't talk like that…" I realized. "Wait a minute. There's a third brother!?" I was in shock. All this time, I thought there was only Sans and Papyrus. Who knew?

Oh. Well, basically all the monsters.

"SANS! WHAT ARE YOU DOING? DON'T SHOW HIM…HER…UM... DON'T SHOW FRISK THE NOTE! ARE YOU BRAINDEAD!? " Papyrus walked into the bar as all the others shushed him.

"relax. it's ok, you can trust her…or, him…what are you huh?" He suddenly turned to me.

"Hehe, that's my secret!" I said with a wink. "You know what else is a secret? HOW YOU LIED TO ME ABOUT A THIRD BROTHER!"

"hey technically, i never said there were only two."

"SO HOW'S ABOUT IT SANS? SHOULD WE BRING…IT…WITH US?" Papyrus asked. I rolled my eyes once he said it. "I FEEL LIKE WE CAN'T LIE ANYMORE OR LEAVE IT BEHIND!"

"eh, why the heck not?" Sans replied.

We went back to Alphys' lab. She was sitting there analyzing some science-y thing. The room was covered in wrinkled papers and posters of anime catgirls. I picked one of the papers up and started to read it.

"Undyne…you are the light of my heart. You are my point of existence. I have no idea what I'd do without you…Undyne…I love y-"

"H-Hey! Stop it!" Alphys grabbed the paper and ripped it in pieces. "Anyways…are you ready to go back to the True Lab, guys?" She finished her work. We all looked at each other and nodded.

"remember kid, once you get in here, all of your understanding of the underground will change, and not for the better." Sans warned.

"ALRIGHT FRISK, ARE YOU READY?" Papyrus asked.

"Let's do this…" I answered.


End file.
